One employee, 47-year-old Clifton Swain of Fayetteville, was killed and four were injured.
Investigators have ruled the incident an accident, but the case is still under investigation.
The leak happened Saturday around 10 a.m. and about 30 employees were working at the time. The names of the four injured workers have not been released.
Two were taken to Cape Fear Valley Hospital and later to the UNC Chapel Hill Burn Center, two were transported to Southeastern Regional Medical Center. One employee was admitted and one was treated and released.